Computational study of 4,4′-dimethoxy triphenylamine donor linked with low band gap π-spacers by single and double bonds for DSSC applications

Abstract

In this work, ten metal-free organic dyes based on the 4,4′-dimethoxy triphenylamine donor and cyanoacrylic acid acceptor were designed and computationally studied for their potential in DSSC. The different π-spacers employed for the comparative study are benzothiadiazole (TC1), quinoxaline (TC2), benzotriazole (TC3), phenathrothiadiazole (TC4) and dihexylcyclopentadithiophene (TC5). The 4,4′-dimethoxy triphenylamine donor was paired with the π-spacers via single-bond/double-bond joints. This computational work mainly aims at determining the impact of the π-spacer on the geometrical and optoelectronic properties using the Density Functional Theory (DFT) and Time-Dependent-DFT approaches. Our studies revealed that all of the designed dyes have strong absorptions in the range of 560–700 nm with satisfactory oscillator strengths and light-harvesting efficiencies (LHE). Several other photovoltaic parameters, such as absorption maximum, driving force for dye regeneration (G_reg), energy level alignment, chemical reactivity parameters, reorganization energy, and dye adsorption energy (E_ads), were measured to determine the role of heterocyclic π-spacers in improving the efficiency of a solar cell. Based on the above parameters, the dye with benzothiadiazole spacer was identified to be the most promising candidate among those studied. These findings provide valuable hints for the fast screening of π-spacers for the efficient molecular engineering of organic sensitizers.